A new lighting scheme on the £259.4 million Southern Link Road in Carlisle is using changing light levels and colour temperatures to reduce energy use and limit the impact of artificial light on the environment
Thorn Lighting, a global supplier of outdoor and indoor luminaires and integrated controls, has supplied 379 R2L2 road luminaires with its NightTune technology for the 8km stretch, which connects Junction 42 of the M6 with the A595 at Newby West.
The scheme was designed to meet the lighting requirements of a major new highway while taking into account the route’s rural setting and the needs of nocturnal wildlife.
Rather than operating at a fixed colour temperature throughout the night, the NightTune system automatically adjusts both the intensity and colour temperature of the lighting according to the time.
From dusk until 9pm, the luminaires operate at 2700K and 100% output. Between 9pm and midnight, output falls to 50% while the colour temperature drops to 2400K. From midnight until 5am, the lighting moves to 2200K before gradually returning to 2700K and full output ahead of dawn.
According to Thorn, reducing light output and shifting towards warmer colour temperatures can reduce the amount of shorter-wavelength blue light introduced into the nocturnal environment.
The approach was specified by Cumberland Council, which wanted to minimise the impact of artificial light on the surrounding landscape and ecology without compromising highway safety.
‘Ecology was part of the brief from the start’
Craig Lensky, Key Account Manager, Outdoor Lighting at Thorn Lighting, says: “What makes this project particularly interesting is that ecology wasn’t treated as something to consider once the road lighting had been designed. It was part of the lighting brief from the beginning. We had to provide the right light for people using a major new road but also think very carefully about what that light was doing beyond it and throughout the night.”
The project required Thorn to develop several customised optical variants of its R2L2 platform to achieve the required road lighting levels across the changing colour-temperature range.
The installation also uses zero-tilt luminaires, while R2L2 is independently DarkSky Approved at colour temperatures of 3000K and below when installed within the relevant approval conditions.
Thorn says the NightTune approach can also deliver energy savings by reducing light levels during periods when traffic and pedestrian activity is lower.
Its comparative spectral analysis found that, against a fixed 3000K dimmable solution using an equivalent dimming programme, a NightTune cycle produces an average blue peak 13% lower and overall low-wavelength output 18% lower.
The Carlisle Southern Link Road opened to traffic in June 2026. Alongside the new carriageway, the project includes walking, wheeling and cycling infrastructure, although part of the shared-use route across the Caldew Crossing has deliberately been left unlit for environmental reasons.
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